wxControlRenderer::DrawLabel() was used by both wxStaticText and wxButton but
their labels may need to be drawn differently and wxRenderer does have
different DrawLabel() and DrawButtonLabel() to do it. Now also add a separate
method for the buttons to wxControlRenderer.
See #11220.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62004 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775